For shows like this, Foxtel are not allowed to begin encoding for On Demand until the first live airing is finished. That's why there's a delay between the first showing and it becoming available on demand.

I found it wasn't available when I wanted to watch it and then came back later to miss the beginning (or actualy I don't know how much I missed. It is very annoying and I notice there are no replies from Foxtel Now. How do you find out what time it will be on again and I do see that it is only available till Oct 2017!

Outlander Season 3 episode 1 is available to view On Demand right now, though not in HD yet. Just use the search function to find it.

To watch it as it airs - it's on at 7.30pm (Sydney time) Mondays on Showcase channel. There are repeats at various times afterwards - ep 1 is repeated at 10.40pm Monday and 12.40am, 1.25pm, 3.25pm, 6.35pm and 8.35pm on Saturday.